'The end of the human race'. On the list of doomsday scenarios that could wipe out the human race, super-smart killer robots rate pretty high in the public consciousness.
All stars live by fusing hydrogen into helium. In the first step of the process, two hydrogen atoms fuse to form deuterium. In the next step, another hydrogen atom fuses with the deuterium, creating a rare isotope of helium that has two protons and one neutron in its nucleus. In the third step, two of the rare helium atoms fuse to create a single normal helium atom and two hydrogen atoms. The fusion pathway described above requires six hydrogen atoms to create one helium atomâhowever, there are two hydrogen atoms left over at the end of the process. The net result is that it takes four hydrogen atoms to make one helium atom.
Stars are fusion engines, and they are powered primarily by fusing the element hydrogen into the element helium (the first and second most abundant elements in the universe, respectively). This process sometimes goes under the name proton-proton reaction.As stars exhaust their hydrogen fuel and build up a lot of helium, they begin to fuse the helium together to form the element carbon in what is called the triple-alpha process. Links are provided to the relevant Wikipedia articles. The threshold temperature of hydrogen fusion (sometimes called a proton-proton reaction) is on the order of 10,000,000 K to 14,000,000 K or 10 to 14 million degrees Kelvin.